adenosine triphosphate

The Columbia Encyclopedia, 6th ed.

Copyright The Columbia University Press

adenosine triphosphate (ATP) (ədĕn´əsēn trī´fŏs´fāt), organic compound composed of adenine, the sugar ribose, and three phosphate groups. ATP serves as the major energy source within the cell to drive a number of biological processes such as photosynthesis, muscle contraction, and the synthesis of proteins. It is broken down by hydrolysis to yield adenosine diphosphate (ADP), inorganic phosphorus, and energy. ADP can be further broken down to yield adenosine monophosphate (AMP), additional phosphorus, and more energy. When the phosphorus and energy are immediately used to drive other reactions, such as the synthesis of uridine diphosphate (UDP), an RNA precursor, from uridine monophosphate (UMP), the pair of reactions are said to be coupled. New ATP is produced from AMP using the energy released from the breakdown of fuel molecules, such as fats and sugars.

Extracellularly, ATP has been found to act as a neurotransmitter. ATP receptors are widespread through the body. On its own it is known to have effects in the arteries, intestines, lungs, and bladder. It is also often released in tandem with other neurotransmitters, perhaps to add chemical stability. See phosphorylation.

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adenosine triphosphate

adenosine triphosphate (ATP): sometimes called ‘the spark of life’. Any bodily movement powered by voluntary or involuntary muscle; other cellular movements such as the migration of white blood cells; the swimming of sperm; and even the contraction of hair cells in the inner ear need a supply of free energy. But so too does the transport of molecules from one body compartment to another, and the synthesis of all biomolecules required for growth, repair, or maintenance of bodily functions. ATP is an energy-rich molecule, which releases free energy when it is broken down to either ADP (adenosine diphosphate) or AMP (adenosine monophosphate). This reaction is usually stimulated by enzymes collectively called ATP-ases. Even a sedentary adult breaks down 40 kg/day of ATP and the rate of consumption rises to 0.5 kg/minute during strenuous exercise. But cells do not store large amounts of ATP, so it must be continually replenished. The energy that must be put back to reconstruct ATP from ADP is supplied by the oxidation (burning) of foods.

Alan W. Cuthbert

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adenosine triphosphate

adenosine triphosphate (ATP) High-energy phosphoric ester (i.e. nucleotide) of the nucleoside adenosine, which functions as the principal energy-carrying compound in the cells of all living organisms. Its hydrolysis to ADP (adenosine diphosphate) and inorganic phosphate is accompanied by the release of a relatively large amount of free energy (34kJ/mol at pH 7) which is used to drive many metabolic functions.

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adenosine triphosphate

adenosine triphosphate (ATP) A high-energy phosphoric ester, or nucleotide, of the nucleosideadenosine which functions as the principal energy-carrying compound in the cells of all living organisms. Its hydrolysis to ADP and inorganic phosphate is accompanied by the release of a relatively large amount of free energy (34 kJ/mol at pH 7) which is used to drive many metabolic functions.

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